The present invention relates to an improved annulus pressure responsive tester valve for use in the flow testing of oil and gas wells.
Various tester valves, circulation valves and sampler valves for testing oil and gas wells have been developed which are responsive to changes in the annulus pressure of the fluid between the well bore and the testing string for the opening and closing of the various valves. These various annulus pressure responsive valves are useful, particularly in offshore testing operations, where it is desired to manipulate the various valves in the testing string without utilizing reciprocation or rotation of the testing string, and thus allows the blowout preventors to remain closed about the testing string during the test.
The assignee of the tester valve of the present invention has recently developed an annulus pressure responsive tester valve which operates in response to a relatively low annulus pressure increase and decrease; this tool is shown in U.S. Pat. Nos. 4,422,506 and 4,429,748. These low pressure responsive tools have a power piston which is exposed to well annulus pressure at its upper end, and which has its lower end exposed to pressurized nitrogen gas in a nitrogen chamber located therebelow in the tool. Located below the nitrogen chamber is a metering chamber or equalizing chamber filled with oil. A floating piston separates the gas in the gas chamber from the oil in the metering chamber. Disposed in the metering chamber is a metering cartridge which provides a resistance to flow of the oil therethrough. The lower end of the metering chamber below the metering cartridge is communicated with well annulus pressure, and a second floating piston separates the oil in the metering chamber from well fluid which enters the lower end of the metering chamber. An increase in annulus pressure is immediately communicated to the upper surface of the power piston, but is delayed for a significant period of time in being fully communicated to the lower side of the power piston, so that a rapid increase in well annulus pressure will cause a downward pressure differential across the power piston to move the power piston and actuate the tool.
A number of modifications of the basic low pressure responsive tool have been developed by the assignee of the present invention as illustrated in U.S. Pat. No. 4,537,258.
One particular feature of such tools to which many of the alternative designs developed by the assignee of the present invention have been directed is the provision of a means for controlling the position of the tester valve during changes in annulus pressure. That is, while the normal operation of the tool provides for opening and closing of the ball valve in response to reciprocating motion of the power piston, it is sometimes desired to be able to maintain the ball valve in either a closed or an open position during changes in annulus pressure. There are several reasons why this feature is desirable. For example, the operator may wish to run the tool into the well with the ball valve in an open position in order to fill the testing string as it is run into the well. Also, it may be desired to pressure test the annulus after the testing string is in position without opening the testing valve. Numerous approaches have been utilized to control movement of the ball valve in a testing tool.
For example, an actuating mandrel associated with the ball valve may be initially shear pinned in place to hold the valve closed while running into a well, as shown for example in FIG. 2B of U.S. Pat. No. 4,422,506.
U.S. Pat. No. 4,429,748 shows in FIG. 2C thereof a resilient ring assembly 206 to positively control the full opening and closing of the ball valve such that the ball valve is prevented from only partially opening or closing.
U.S. Pat. No. 4,537,258 discloses several embodiments of such tools. The embodiment disclosed in FIGS. 2A-2E and FIG. 3 thereof utilizes a lug and slot arrangement disposed between the power piston and the housing for controlling movement of the power piston relative to the housing. The embodiment disclosed in FIGS. 5A-5G thereof uses a spring loaded pin and detent arrangement 600 for locking the actuating mandrel in a position corresponding to an open position of the ball valve.
U.S. Pat. No. 4,355,685 shows a circulating valve having an annulus pressure responsive operating means similar to that of the tools just discussed, and including a lug and slot arrangement disposed between the power piston and the housing as seen in FIG. 1C and FIG. 4 thereof for controlling the position of the power piston relative to the housing. Another device recently developed by the assignee of the present invention is a multi-mode testing tool shown in U.S. Pat. 4,633,592. It is noted that the aforesaid, '592 patent is itself not prior art to the present invention; that application is being referred to only as a convenient means for describing one embodiment of the tool shown therein which is a part of the prior art. U.S. Pat. No. 4,633,592 shows several embodiments of a ratchet means for operably connecting an actuating mandrel to a power piston but only the embodiment shown in FIG. 10 thereof is a part of the prior art. The ratchet means disclosed in FIG. 10 in '592 patent is similar in some respects to the ratchet means utilized in the tester valve of the present invention.